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Abstract

Background—Cardiovascular diseases are the major cause of mortality among both men and women with a lower incidence in women before menopause. The clinical use of doxorubicin, widely used as an antineoplastic agent, is markedly hampered by severe cardiotoxicity. Even if there is a significant sex difference in incidence of cardiovascular disease at the adult stage, it is not known whether a difference in doxorubicin-related cardiotoxicity between men and women also exists. The objective of this work was to explore the cardiac side effects of doxorubicin in adult rats and decipher whether signaling pathways involved in cardiac toxicity differ between sexes.

Methods and Results—After 7 weeks of doxorubicin (2 mg/kg per week), males developed major signs of cardiomyopathy with cardiac atrophy, reduced left ventricular ejection fraction and 50% mortality. In contrast, no female died and their left ventricular ejection fraction was only moderately affected. Surprisingly, neither global oxidation levels nor the antioxidant response nor the apoptosis signaling pathways were altered by doxorubicin. However, the level of total adenosine monophosphate–activated protein kinase was severely decreased only in males. Moreover, markers of mitochondrial biogenesis and cardiolipin content were strongly reduced only in males. To analyze the onset of the pathology, maximal oxygen consumption rate of left ventricular permeabilized fibers after 4 weeks of treatment was reduced only in doxorubicin-treated males.

Introduction

Cardiovascular diseases are the major cause of death globally. Several studies show sex differences in morbidity and treatment efficacy in patients with cardiovascular disease; thus highlighting the need for sex-specific therapy.1,2 It is well accepted that women develop less cardiovascular disease or maintain better cardiac function than do men at least before menopause, in part, because of differences in the hormonal status, but not exclusively.2,3 Nevertheless, sex differences in cardiovascular pathophysiology have been poorly studied to date.3

Anthracyclines remain among the most potent anticancer drug. They are an important component of numerous chemotherapy protocols of both hematologic malignancies and solid tumors. However, their clinical use is hampered by the risk of severe cardiotoxicity, which may lead to a progressive cardiomyopathy that may evolve to congestive heart failure. Cardiotoxicity refers to deleterious and unwanted side effects of therapeutic compounds on heart function. There are several risk factors for cardiotoxicity induced by anthracyclines, such as total cumulative dose, additional treatment, existing cardiomyopathy, age, and sex.4 However, doxorubicin-related sex differences in cardiotoxicity have been underanalyzed. One study showed that male patients with lymphoma treated with doxorubicin showed a greater subclinical late cardiomyopathy when compared with female patients.5 Experimental studies lack information because most work has been conducted in males,6 but some studies suggest that females may develop less severe doxorubicin-induced cardiomyopathy and nephropathy than males.7–9 Investigation of protective mechanisms operating in female organisms could be a promising approach in searching for new therapeutic tools.

Deficits of mitochondrial function, biogenesis, and energy metabolism have recently emerged as key contributors to heart failure.10,11 Interestingly, mitochondrial alterations also seem to be involved in doxorubicin-mediated cardiotoxicity.12,13 Moreover, alterations in energy signaling pathways, such as the AMP-activated protein kinase (AMPK), have been recently shown to be involved in doxorubicin cardiotoxicity,12 but possible sex differences have not yet been evaluated.

The aim of this study was therefore to (1) examine sex-specific doxorubicin cardiotoxicity, (2) to investigate energy metabolism, and (3) to identify signaling pathways that could be involved in these differences.

Methods

Methods are available in the Data Supplement.

Animal Conditioning

A chronic model of doxorubicin was chosen by weekly intravenous injection of 2 mg/kg doxorubicin or saline solution during 7 weeks in 16 male and 12 female adult Wistar rats (Janvier Laboratories). Analysis of doxorubicin 2 hours after intravenous injection showed similar level of doxorubicin in hearts from male and female rats (male, 7.9±0.6; female, 8.2±1.6 ng doxorubicin/mg dry weight). Because of ethical concerns of doxorubicin-treated males at 7 weeks (20% loss of initial weight, prostration, and 50% mortality), the number of rats could not be enlarged. For experiments aimed at characterizing early dysfunction, animals were treated for 4 weeks (20 females and 20 males). Animal experimental procedures were approved by the Animal Ethics Committee of Paris-Sud University. Investigations were done in accordance with European Community legislation relating to the care and use of animals (Directive 2010/63/EU), and the corresponding French legislation (French decree 2013–118 du 1er février 2013).

Statistical Analysis

Data are expressed as mean±SEM unless specified. The survival of the animals was analyzed by the Kaplan–Meier method. The weight loss of the animals was analyzed by a 2-way repeated measures ANOVA (normal distribution [Shapiro–Wilk test] and homogenous variance verified). Two-way ANOVA was used to study the global effect of sex and treatment, followed by Student–Newman–Keuls post hoc test to determine individual differences (normal distribution [Shapiro–Wilk test] and homogenous variance verified). Pearson correlation was performed. P values (2 sided) are presented to 3 decimal places if significant ant 2 if not. Statistical significance between NT and doxorubicin group was defined as P<0.05 (*), P<0.01 (**), and P<0.001 (***).

Results

Females Have Better Survival and Minor Body Mass Loss When Compared With Males After 7 Weeks of Doxorubicin

After 7 weeks of doxorubicin treatment, female rats survived and had normal appearance. However, doxorubicin induced a severe toxicity among males with 50% mortality (Figure 1A). These animals were less active with poor appetite, had a significant weight loss over time (Figure 1B), and slowing of growth together with severe cardiac and splenic atrophy (Table). Both sexes had enlarged liver, pale, and swollen kidneys and increase in triglycerides and cholesterol serum content. To note, none of the treated rats presented cardiac hypertrophy. Overall, females were much less affected than males as evidenced by the significant interaction between sex and treatment effects on the body, and heart weight, lung, kidney and tibia length (Table).

Only Males Present Important Signs of Heart Failure After 7 Weeks of Doxorubicin Treatment

Gross examination of treated males revealed the presence of ascites, pleural effusion, and increased lung weight indicating heart failure in surviving animals, suggesting that the sickest hearts may have been missed because of lethality. Left ventricular levels of atrial natriuretic factor (Anf), interleukin-6 (Il-6), and myocyte-enriched calcineurin-interacting protein (Mcip1) mRNA, markers of myocardial stress, were more upregulated in treated males than in females (Figure 1C). Histological assessment of male and female heart (Figure 1D and 1E) revealed that while perimyocyte fibrosis was similar in both sexes, total level of fibrosis and reactive fibrosis was more important in doxorubicin-treated males (Figure IA–ID in the Data Supplement). We noticed inflammatory infiltrate in treated animals, but accumulation of vacuoles and important myolysis were specific to treated males (Figure 1E). Echocardiography showed a strong reduction of the fractional shortening and left ventricular ejection fraction (LVEF) for treated males from 87.5±2.0 to 55.9±0.6% (P<0.0002), whereas female LVEF was only moderately affected (86.3±2.3–79.0±1.4%; P<0.01; Figure 2A). Similarly, sex difference after doxorubicin treatment was observed for the systolic LV internal diameter with an increase only for males. Lower diastolic LV internal diameter in females when compared with males was not changed by doxorubicin. The interventricular septal wall thickness in diastole was similar in both sexes and was not modified by doxorubicin treatment, whereas in males the drug reduced interventricular septal wall thickness in systole. Cardiac output was different between sexes and decreased only in treated males. All cardiac parameters present significant statistical interactions between sex and doxorubicin effects, except for diastolic parameters and cardiac output normalized to body weight (Figure 2B). These results combined with mortality, anatomic, and histological data reveal a sex-related cardiomyopathy difference with a worse cardiac function for doxorubicin-treated males.

Death Signaling Pathways and Oxidative Stress Are Similar in Doxorubicin-Treated Males and Females

To investigate the mechanism of sex-dependent responses to doxorubicin, we first analyzed cell death. We observed a greater increase in global cell death in male than in female hearts (Figure 3A; Figure IE and IF in the Data Supplement). However, cardiomyocyte TUNEL staining was similar in both sexes (Figure 3A), but inflammatory infiltrate cells were highly TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labelling) positive in treated males. The absence of sex difference in doxorubicin-induced cell death was confirmed in adult cardiomyocytes isolated either from male or female rats (Figure 3B and 3C). The percentage of viable cells was only 32±4% after 24 hours of doxorubicin treatment when compared with 72±2% for nontreated cells, and no difference was observed between male or female cardiomyocytes. Doxorubicinol, the main metabolite of doxorubicin, was slightly more toxic because viability was only 15%; once again no sex difference was observed (data not shown). Furthermore, gene expression of cell death, endoplasmic reticulum stress, and autophagy markers was studied. Tumor necrosis factor-α (Tnfα), Bcl2, Beclin, Chop, and Grp78 did not differ between sexes or after doxorubicin treatment (Figure 3D). Superoxide dismutase 2 (Sod2) and catalase (Cat) but not glutathione peroxidase 1 (Gpx1) gene expression were also altered in both sexes after doxorubicin treatment (Figure 3E), but no sex difference was observed for these reactive oxygen species detoxification enzymes. Surprisingly, global protein carbonylation was comparable in all rat groups (Figure 3F; Figure II in the Data Supplement), with a slight trend for lower level in females and higher level in doxorubicin-treated animals. Overall, these results suggest that death signaling pathway and oxidative stress are not primarily involved in the sexual dimorphism of doxorubicin cardiotoxicity.

Previous studies showed the importance of AMPK in the cardiotoxicity of anthracyclines, but these were conducted only in males.12,14 To elucidate whether the sex-dependent doxorubicin cardiotoxicity difference could be linked to AMPK signaling, we analyzed the level of total and phosphorylated AMPK and acetyl-CoA carboxylase, its downstream target. An important decrease of total AMPK (55%), total acetyl-CoA carboxylase (57%), and phosphorylated acetyl-CoA carboxylase (61%) was present in doxorubicin-treated males. Importantly, this was not the case for the doxorubicin-treated females (Figure 4A). Because AMPK is a central regulator of both lipid and glucose metabolism, we analyzed gene expression involved in glucose and fatty acid utilization in the left ventricle. There was an important decrease in the expression of the glucose transporter Glut4 and of hexokinase 2 (Hk2), which significantly correlated to total AMPK (R=0.55; P=0.04 and R=0.70; P=0.003, respectively), whereas pyruvate dehydrogenase kinase 4 (Pdk4) expression increased in doxorubicin-treated males (Figure 4B), pointing to a decrease in carbohydrate metabolism. For the treated females, no or a small reduction of the glucose metabolism genes was observed. Although total lactate dehydrogenase activity was preserved (Figure 4D), a significant decrease of H and increase of M-lactate dehydrogenase isoform were observed only in males treated with doxorubicin (Figure IIIA in the Data Supplement). About lipid metabolism, no sex difference was noticed in the decrease of carnitine palmitoyltransferase 1b (Cpt1b) and medium-chain acyl-CoA dehydrogenase (Mcad) induced by doxorubicin treatment (Figure 4C). These results showed that doxorubicin induced a deregulation of cardiac energy homeostasis in males, whereas normal energy metabolism is maintained in females. Cardiac energy homeostasis appeared as one of the sites of sex differences as evidenced by significant statistical interactions between sex and treatment effects (Table I in the Data Supplement).

Doxorubicin Severely Impairs Mitochondrial Biogenesis in Males

No significant changes were observed in citrate synthase (CS), cytochrome oxidase (COX), and total and mitochondrial creatine kinase (CK) activities in both sexes after 7 weeks of doxorubicin treatment (Figure 4D; Figure IIIB in the Data Supplement). Nevertheless, a trend for COX and CK activities was noticed for treated males (Figure 4D). We analyzed protein and mRNA levels of the transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator1 (Pgc-1s), master regulators of mitochondrial biogenesis, and their downstream targets. No modification of PGC-1α protein level was observed; however, mRNA levels of Pgc-1α and its homologue Pgc-1β were strongly reduced only in doxorubicin-treated males (Figure 5A and 5B). Downstream genes involved in mitochondria biogenesis were highly downregulated in treated males, whereas the deregulation was moderate or even absent (such as transcription factor A mitochondrial Tfam) in the treated females (Figure 5B). No effect of doxorubicin was observed in females for COX subunit IV isoform1 (Cox4) and optic atrophy 1 (Opa1) gene expression, whereas there was a strong decrease in treated males. For both sexes, adenine nucleotide translocator 1 (Ant1), voltage-dependent anion channel 1 (Vdac1), Cs, and mitofusin2 (Mfn2) were strongly decreased (Figure 6A). However, we did not observe variation in the level of the electron transport chain proteins and other mitochondrial proteins content (Figure IIIC in the Data Supplement). Because AMPK and more recently PGC-1α/β have been shown to regulate cardiolipin homeostasis, the cardiolipin content was measured.15,16 A strong reduction was revealed only in doxorubicin-treated males (Figure 6B). Mitochondrial biogenesis and cardiolipin environment emerged as other key sites of doxorubicin-related sex differences because there is a significant statistical interaction between sex and treatment effects (Table I in the Data Supplement). Taken together, these results show that mitochondrial biogenesis is a specific target of doxorubicin in males.

Early Cardiac Dysfunction in Males Is Linked to Altered Mitochondrial Function

To unravel the onset of cardiac dysfunction, we shortened the experiments to 4 weeks of doxorubicin treatment. Once again, treated females had minor anatomic and no cardiac alterations, whereas treated males developed major signs of cardiomyopathy with cardiac atrophy, reduced LVEF, increased levels of Anf and Il6 (Table II in the Data Supplement; Figure 7A). Surprisingly, Pgc-1α mRNA level was similar in all groups, whereas Pgc-1β was reduced only in doxorubicin-treated males (Figure 7B). To investigate mitochondrial physiology, the activity of the respiratory chain and the ability of mitochondria to oxidize different substrates were studied in left ventricular permeabilized fibers at 4 weeks by measuring oxygen consumption rates (Figure 7C). No alteration was observed in treated females. In contrast, respiration rate with malate+palmitoyl-CoA+carnitine was reduced in treated males from 13.6±1.1 to 10.7±0.5 µmol O2/min per gram dry weight (P<0.04; Figure 7C). Similarly, the maximal oxygen consumption rate in the presence of mitochondrial substrate’s mixture (malate+palmitoyl-CoA+carnitine, +pyruvate, +glutamate and succinate) was reduced only in doxorubicin-treated males from 24.5±1.5 to 19.6±1.0 µmol O2/min per gram dry weight (P<0.05). We analyzed mitochondrial DNA content normalized to nuclear DNA (Figure 7D). Again, we observed a decrease for doxorubicin-treated males only. Finally, global protein acetylation in the left ventricles (Figure 7E) was reduced only for doxorubicin-treated males (male NT 0.21±0.02 acetylation level normalized to coomassie versus 0.13±0.01 male doxorubicin [P=0.003]; female NT 0.17±0.02 versus 0.18±0.01 female doxorubicin). Altogether, these results suggest that mitochondrial dysfunction participates in early cardiotoxicity in males and in sex-related differences as shown by the interaction between sex and doxorubicin for mitochondrial function (Figure 7F).

Discussion

In the present study, we explored sexual dimorphism of doxorubicin cardiotoxicity and energetic and signaling pathways that could be involved in these differences. Two clinically relevant cumulative doses of doxorubicin, either 14 mg/kg after 7 injections or 8 mg/kg after 4 injections were administrated to investigate sex differences in the cardiotoxicity of doxorubicin. Doxorubicin treatment resulted in sex differences characterized in males by (1) important weight loss and decrease in survival rate, (2) strong alterations of myocardial function, (3) decrease in energy signaling pathways, (4) downregulation of mitochondrial biogenesis, (5) decrease in cardiolipin content, (6) decrease in mitochondrial DNA content, and (7) and alteration of mitochondrial respiration. No sex differences were found for the oxidative stress response or for death markers, whereas mitochondrial dysfunction and mitochondrial protein expression were associated with early cardiotoxicity in males.

Several clinical studies and animal models indicate that dose-dependent doxorubicin cardiotoxicity increases with age.17,18 Colombo et al19 showed that chemotherapy with anthracycline results in higher toxicity in 24-month-old when compared with 6-month-old-rats. Three-month-old male rats are far more sensitive to doxorubicin than age-matched females. The mortality rate was as high as 50% in males after 7 weeks of treatment, whereas all females survived. Hepatomegaly appeared slightly more important in females; however, liver aspect was identical in both sexes. Similarly, liver weight increase, probably attributable to cellular proliferation, was higher in females than in males.8 The authors showed that the liver oxidative defense system was far less susceptible to in vivo doxorubicin treatment in female than in male rats.8 As expected, doxorubicin treatment induced dyslipidemia in both sexes. However, it was mild at 4 weeks in females and increased thereafter, whereas it was already high at 4 weeks in males.

The present results clearly evidence early signs of cardiac dysfunction and heart failure only in males with cardiac atrophy, which is a hallmark of anthracycline toxicity.20–22 Females had an almost preserved LVEF, whereas males had a severe decrease in LVEF combined with pulmonary edema, ascites, structural myocardial alterations including myolysis and fibrosis and high levels of Il-6, Anf, and Mcip1 mRNA, which have all been correlated with the severity of left ventricular dysfunction.23,24 Thus, females are better protected from doxorubicin-induced heart failure.

Oxidative stress leading to increased cell death has been widely reported as a key mechanism in the development of doxorubicin toxicity25,26 although antioxidant therapy in humans was not able to prevent heart failure induced by anthracyclines.4,27,28 Females may produce less mitochondrial free radicals and have a higher content of antioxidant enzymes than males; these differences having been suggested as a mechanism promoting longevity and preventing cardiovascular diseases.29 Estrogen receptors and their signaling cascades have been implicated in the control of antioxidant enzyme expression.30 However, in our model, doxorubicin did not induce obvious global protein oxidation or sex difference in this parameter. Moreover, level of Gpx1 was unchanged. Nevertheless, decreased levels of Sod2 and Catalase were more important in males after doxorubicin. Recent data reinforced the role of mitochondrial iron accumulation and cellular reactive oxygen species in doxorubicin cardiotoxicity.31,32 The redox balance is certainly altered after doxorubicin treatment. However, the level and importance of oxidative stress are surely time, species, and concentration dependent leading to different results according to the model of doxorubicin treatment.4,14,27,28,31,32 Cardiomyocyte loss through various cell death signaling pathways linked to oxidative stress and DNA damage and mitochondrial alterations has been described in doxorubicin cardiotoxicity.28,33 However, depending on in vitro and in vivo analyses, the results were not always consistent.34,35 In the present study, no sex difference in cell death was observed in vivo and in vitro after doxorubicin. These results match those of the gene expression analysis of cell death markers that did not change in both sexes after doxorubicin treatment. Absence of sex difference in the apoptosis signaling transduction cascade was already reported in vivo after a single IP injection of 10 mg/kg of doxorubicin although this study did not describe cardiac damage in both sexes.36 Thus, neither oxidative stress nor cell death seems to be a strong determinant of sexual dimorphism in doxorubicin cardiotoxicity.

Mitochondrial dysfunction has been recently highlighted as a major determinant of anthracycline cardiotoxicity.13 Moreover, energy depletion and mitochondrial dysfunction are well-known characteristics of the failing heart.10,11 After transverse aortic constriction in mice, better preserved cardiac function in females is associated with lower alteration of mitochondrial function and biogenesis, as well as fatty acid oxidation.37 This was explained by the transcriptional control of Pgc-1α gene expression by estradiol.37 Indeed, mitochondrial function and biogenesis are under the control of estrogens.30 Moreover, PGC-1α and PGC-1β modulate estrogen receptor α transcriptional activity.38 It thus seems that there is a tight relationship among PGC-1s, mitochondrial functions, and female sex hormones. Indeed, doxorubicin treatment also altered mitochondria more severely in males, as evidenced by the downregulation of gene expression of mitochondrial biogenesis (Pgc-1s and their downstream transcription cascade), mitochondrial function (Cox, Cs, PTP members) and mitochondrial dynamic (Mfn2 and Opa1), decreased mitochondrial respiration, and mitochondrial DNA content. PGC-1s have been characterized as orchestrators for mitochondria biogenesis, substrate preference, and antioxidant defenses.39 PGC-1α and its targets are downregulated in different experimental models of heart failure and in patients.40,41 The same was found in daunorubicin-treated male rabbits.14 In the present study, PGC-1β seemed a relevant target of doxorubicin in males because its downregulation is also observed at the onset of cardiac toxicity. PGC-1β discovered a decade ago, is expressed predominantly in skeletal muscle, heart, brain, and brown adipose tissue.42,43 In pressure-overload hypertrophy, PGC-1β was described as an important factor in maintaining mitochondrial function by preserving glucose metabolism44 and could be a key parameter in sex-related doxorubicin cardiotoxicity differences. The pivotal role played by mitochondrial dysfunction in doxorubicin cardiotoxicity is, furthermore, revealed by the fact that activation of mitochondrial function or biogenesis by various agents, such as frataxin overexpression, exercise training or resveratrol, are sufficient to protect against doxorubicin cardiotoxicity and cardiac dysfunction.45,46 In the present study, doxorubicin cardiotoxicity was observed only in males and was accompanied by early mitochondrial dysfunction again emphasizing the role of mitochondrial dysfunction in doxorubicin cardiotoxicity and further suggesting a possible role in sex differences.

Finally, AMPK, a kinase activated by the low-energy status, has been reported to be a cardiac target of doxorubicin.12 Activation of AMPK via upregulation of adiponectin, a hormone secreted by adipose tissue, or via treatment with metformin, an antidiabetic drug, improved the energy state, mitochondrial function, and cardiac contractility altered by doxorubicin.47,48 Once activated, AMPK stimulates ATP production and inhibits ATP-consuming processes and is a key factor for the regulation of mitochondrial biogenesis.49 In treated males but not in females, AMPK, its important target acetyl-CoA carboxylase, and gene expression of proteins involved in glucose and fatty acid use were downregulated. Importantly, a sex difference was observed in glucose metabolism as evidenced by Pdk4 and M-lactate dehydrogenase increase, converging toward impairment of oxidative metabolism in males. AMPK may have a potential cardioprotective role in females by limiting glucose metabolism alteration and maintaining normal mitochondrial biogenesis. Interestingly, a significant correlation was found between Pgc-1β and total AMPK (R=0.62; P=0.01). Moreover, these 2 pathways also control cardiolipin homeostasis. Interestingly, several studies have shown that doxorubicin binds with high affinity to cardiolipin.50 We previously showed that AMPK regulates cardiolipin synthesis and remodeling.15 Recently, PGC-1α/β were also described as cardiolipin synthesis modulators.16 These data are in accordance with our results showing that doxorubicin-treated males displayed almost normal in vitro mitochondrial protein content and activity, whereas in situ oxidative capacity are reduced probably because of altered cardiolipin environment of the respiratory chain.

At present, clinical studies aimed at analyzing the difference between sexes with respect to cardiotoxicity caused by anticancer therapy are still sparse. This study has unraveled a significant sexual dimorphism in the sensitivity to doxorubicin in rats. Mitochondrial dysfunction and altered energy signaling pathways together with altered cardiolipin homeostasis seem to play a pivotal role in doxorubicin cardiotoxicity and sex differences (Figure IV in the Data Supplement). A cause–effect relationship between altered AMPK activity and sex differences in cardiotoxicity, as well as the role of sex hormones, remain to be established. Additional investigations are needed to decipher the upstream mechanisms of energy metabolism remodeling in males to define novel therapeutic targets to prevent anthracycline cardiotoxicity.

Acknowledgments

We thank Valérie Domergue and Pauline Robert (Animal facility of IPSIT-IFR141 [Institut Paris-Sud d'Innovation Thérapeutique - Institut Fédératif de Recherche]) for their help with the animals, Claudine Deloménie (Transcriptomic platform of IPSIT-IFR141) for her expertise in molecular biology, Eric Jacquet and Prishila Ponien (Platform Imagif, Centre National de la Recherche Scientifique Gif/Yvette) for TLDA TaqMan Low Density Array experiments. We thank Nicolas Raymond for his excellent histological work and the Microscopy Facility of the Centre Chirurgical Marie Lannelongue. We thank Antoinette Lemoine, Assistance Publique-Hôpitaux de Paris, Hôpital Paul Brousse for help with doxorubicin. We thank Matthieu Gutmann, Christophe Lemaire, Eric Morel, Pierre Chaminade, Jean-Louis Paul, Vincent Algalarrondo (Université Paris-Sud) for helpful discussion and Rodolphe Fischmeister for continuous support. We finally thank Jesse Schloegel for careful reading of the article.

Sources of Funding

Our laboratory is a member of the Laboratory of Excellence LERMIT (Laboratoire d'Excellence en Recherche sur le Médicament et l'Innovation Thérapeutique) and is supported by a grant from Fondation pour la Recherche Médicale, Université Paris-Sud (ERM) and CORDDIM and MALINF-DIM Ile de France. MM is recipient of a fellowship from the Fondation ARC. RVC is senior scientist at CNRS.

. Control by circulating factors of mitochondrial function and transcription cascade in heart failure: a role for endothelin-1 and angiotensin II.Circ Heart Fail. 2009;2:342–350. doi: 10.1161/CIRCHEARTFAILURE.108.812099.

CLINICAL PERSPECTIVE

One of the multiple factors leading to cardiomyopathy and heart failure is anticancer therapy. Doxorubicin, an efficacious anticancer chemotherapeutic, belongs to the World Health Organization list of essential medicines (18th edition, April 2013). However, clinical practices are limited because of safety linked to the dose-dependent cardiac deleterious effects of doxorubicin. Mitochondrial alterations and energy signaling are shown to be involved in heart failure, including doxorubicin-mediated cardiotoxicity. Studies in humans have often shown sex differences in the prevalence and the outcome of cardiovascular disease. We thus investigated the possible sex-specificities in doxorubicin cardiotoxicity development and in the signaling pathways involved in this pathology. We found that after 7 weeks of doxorubicin treatment female Wistar rats had preserved cardiac and mitochondrial function but male rats exhibited poor cardiac function, significant cardiac myolysis, and fibrosis. Total adenosine monophosphate–activated protein kinase, markers of mitochondrial biogenesis, and cardiolipin were decreased especially in males after doxorubicin. Energy signaling pathways thus appear as a critical mediator of sex difference in doxorubicin cardiotoxicity. Additional basic research and clinical studies are both necessary to unravel the pathophysiological differences between females and males to understand the potential relevance to humans. Understanding why mitochondria from female rats are more resistant to this toxic insult may allow development of new pharmacological approaches able to protect this key energetic organelle and ultimately cardiac function.